using System;

    public struct float3

    {

        public float r;

        public float g;

        public float b;

        public float3(float x, float y, float z)

        {

            r = x;

            g = y;

            b = z;

        }

    }

    public struct float4

    {

        public float r;

        public float g;

        public float b;

        public float a;

        public float4(float x, float y, float z, float w)

        {

            r = x;

            g = y;

            b = z;

            a = w;

        }

    }           

public class Program

{

    static float clamp(float val, float min, float max)

    {

        if(val < min) return min;

        if(val > max) return max;

        return val;

    }

    static float max(float a, float b)

    {

        if(a > b) return a;

        return b;

    }

    static float ceil(float a)

    {

        return (float)Math.Ceiling(a);

    }

    static float round(float a)

    {

        return (float)Math.Round(a);

    }

​

    static int GetColorId(float4 maskColor)

    {

        float3 clampedColor = new float3(clamp(maskColor.r - 0.25f, 0.0f, 1.0f), clamp(maskColor.g, 0.0f, 1.0f), clamp(maskColor.b, 0.0f, 1.0f));

         float val = max(clampedColor.r, max(clampedColor.g, clampedColor.b));

         float axisIndex = ceil(clampedColor.r) + ceil(clampedColor.b) * 2.0f;

        return (int)clamp(round(ceil(axisIndex * 4.0f) + ceil(val * 4.0f)), 0, 11);

    }

    public static void Main()

    {

        Console.WriteLine("4 : " + GetColorId(new float4(0.2f, 0.0f, 0f, 0f)));

        Console.WriteLine("5 : " + GetColorId(new float4(0.4f, 0.0f, 0f, 0f)));

        Console.WriteLine("6 : " + GetColorId(new float4(0.6f, 0.0f, 0f, 0f)));

        Console.WriteLine("7 : " + GetColorId(new float4(0.8f, 0.0f, 0f, 0f)));

        Console.WriteLine("");

        Console.WriteLine("0 : " + GetColorId(new float4(0.0f, 0.2f, 0f, 0f)));

        Console.WriteLine("1 : " + GetColorId(new float4(0.0f, 0.4f, 0f, 0f)));

        Console.WriteLine("2 : " + GetColorId(new float4(0.0f, 0.6f, 0f, 0f)));

        Console.WriteLine("3 : " + GetColorId(new float4(0.0f, 0.8f, 0f, 0f)));

        Console.WriteLine("");

        Console.WriteLine("8 : " + GetColorId(new float4(0.0f, 0.0f, 0.2f, 0f)));

        Console.WriteLine("9 : " + GetColorId(new float4(0.0f, 0.0f, 0.4f, 0f)));

        Console.WriteLine("10 : " + GetColorId(new float4(0.0f, 0.0f, 0.6f, 0f)));

        Console.WriteLine("11 : " + GetColorId(new float4(0.0f, 0.0f, 0.8f, 0f)));

    }

}